I have a shelf of Perl books which I find useful. I probably refer to that shelf about once a month. My choice between books and on-line depends on the question. Perl's own documentation is clearly the best place to get accurate, up-to-date answers to specific questions. ("How do I initialize a 'state' variable?") However, if you have completely forgotten the word 'state', but only remember that Perl has a feature similar to C's 'static', your book has a huge advantage. (Skim a few pages on scoped variables.) Once you know what you are looking for, it is a good idea to check the docs. Add a margin note to your book if you find a difference. Add an entry to the index -- You probably are going to need this again some time in the future.
